Name: synthesis and exfoliation of discotic zirconium phosphates to obtain colloidal liquid crystals
Uploaded: 2016-05-25T13:00:00
Description: Watch this Scientific Journal Video about Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals at JoVE.com

This work is partially supported by NSF (DMR-1006870) and NASA (NASA-NNX13AQ60G). X. Z. Wang acknowledges support from the Mary Kay O'Connor Process Safety Center (MKOPSC) at Texas A&amp;M University. We also thank Min Shuai for her guidance.

1. Synthesis of &#945;-ZrP Using Hydrothermal Method
<ol>
	<li>Dissolve 6&#160;g of zirconyl chloride octahydrate (ZrOCl2&#183;8H2O) in 3.75&#160;ml deionized (DI) water in a 150 ml round bottom flask.</li>
	<li>Add 48&#160;ml of 15&#160;M phosphoric acid (H3PO4) dropwise to the ZrOCl2 solution prepared in step 1.1 followed by adding 8.25 ml&#160; deionized (DI) water under vigorous stirring.</li>
	<li>Pour resulting gel-like mixture into Teflon-lined pressure vess...

<ol>
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The reflux method is a good option for making a smaller size of &#945;-ZrP with a uniform diameter and thickness. Similar to the hydrothermal method, the reflux method is limited by the preparation time. In general, it takes longer time for the crystals to grow.
The longer reaction time required for reflux method may result in nanodisks with a larger size. The average size of exfoliated nanodisks is measured by dynamic light scattering (DLS). In this study, the size of exfoliated ZrP nanodisks...

Discotic colloids are naturally abundant in the form of clay, asphaltene, red blood cells, and nacre. A range of applications in many engineered systems, including polymer nanocomposites1, biomimetic materials, functional membranes2, discotic liquid crystal studies3 and Pickering emulsion stabilizers4 are developed based on discotic colloidal nanodisks. Nanodisks with uniformity and low polydispersity is important for studying phases and transformations of liquid crystals. Zirconium phosphate (ZrP) is a synthetic nanodisks with well-ordered layered structure and controllable aspect ratio (thickness over diameter). Therefore, the exploration of different synthesis of ZrP helps to establish fundamental understanding of discotic liquid crystal system.
The structure of ZrP was elucidated by Clearfield and Stynes in 19645. For the synthesis of layered crystals of ZrP, hydrothermal and reflux methods are commonly adopted6,7. Hydrothermal method gives a good control on size ranging from 400 to 1,500 nm and polydispersity within 25%6, while reflux method gives smaller crystals for the same duration time. Microwave heating has been proven to be a promising method for synthesis of nanomaterials8. However, there are no papers describing synthesis of ZrP based on microwave-assisted route. The effective control over size, aspect ratio, and mechanism of the crystal growth by hydrothermal method was systematically studied by our group6.
ZrP can be easily exfoliated into monolayers in aqueous suspensions, and the exfoliated ZrP have been well established as liquid crystal materials in Cheng&#39;s group3,9-13. So far, exfoliated ZrP nanodisks with various diameters, say different aspect ratios, have been studied to conclude that larger ZrP had the I (isotropic)-N (nematic) transition at lower concentration compared to smaller ZrP3. The polydispersity3, salt9 and temperature10,11 effects on the formation of nematic liquid crystal phase have been also considered. Moreover, other phases, such as sematic liquid crystal phase, have been investigated as well13,14.
In this article, we demonstrate experimental realization of such a colloidal ZrP nanodisks suspension. Layered ZrP crystals are synthesized via different methods, and then are exfoliated in aqueous media to obtain monolayer nanodisks. At the end, we show liquid crystal phase transitions exhibited by this system. A notable aspect of these disks is their highly anisotropic nature that the thickness to diameter ratio is in the range of 0.0007 to 0.05 depending on the size of disks3. The highly anisotropic monolayer nanodisks establish a model system to study phase transitions in the suspensions of nanodisks.

<table border="0" cellpadding="0" cellspacing="0" height="202" width="928">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:209px;">Material</td>
			<td style="width:208px;"></td>
			<td style="width:164px;"></td>
			<td style="width:352px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Zirconyl Chloride Octahydrate</td>
			<td>Fischer Scientific (Acros Organics)</td>
			<td>AC20837-5000</td>
			<td>98% +&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">o-Phosphoric Acid</td>
			<td>Fischer Scientific</td>
			<td>A242-1</td>
			<td>&#62;= 85 %</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetra Butyl Ammonium Hydroxide</td>
			<td>Acros Organics (Acros Organics)</td>
			<td>AC176610025</td>
			<td>40% wt. (1.5M)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reaction Oven</td>
			<td>Fischer Scientific</td>
			<td>CL2 centrifuge</td>
			<td>Isotemperature Oven (Temperature Upto 350&#160;C)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge&#160;</td>
			<td>Thermo Scientific</td>
			<td>Not Available&#160;</td>
			<td>Rotation Speed : 100 - 4000 rpm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microwave Reactor</td>
			<td>CEM Corporation</td>
			<td>Discover and Explorer SP</td>
			<td>Temp. Upto 300oC, Power upto 300W, Pressure upto 30bar</td>
		</tr>
	</tbody>
</table>

synthesis and exfoliation of discotic zirconium phosphates to obtain colloidal liquid crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

Figure 1a-c show SEM images of &#945;-ZrP nanodisks obtained from hydrothermal, reflux, and microwave-assisted methods, respectively. It was observed that &#945;-ZrP nanodisks show hexagonal in shape and different thickness depending on synthesis conditions and prepared methods. A previously reported study from our group6 suggests that for the crystal growth time 48 hours or above, the edge of the disks become sharper. Usually, the reflux method yields nanodisk...

Watch this Scientific Journal Video about Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals at JoVE.com

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

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